ST. LOUIS – Astros manager Bo Porter called the media back into his office late Wednesday and delivered the news: Jarred Cosart had a direct ticket to the Show.

After Cosart went out of his way during spring training to say he wanted a spot on the Astros’ opening-day roster, one of the rebuilding organization’s most promising pitching prospects is scheduled to start Friday against Tampa Bay ace lefthander David Price, who won the 2012 American League Cy Young award.

Cosart, 23, went 7-4 with a 3.29 in 18 games (17 starts) for Class AAA Oklahoma City this season. The 6-foot-3, 180-pound righthander struck out 93, allowed 74 hits and walked 50 in 93 innings.

Cosart is ranked as the Astros’ No. 7 overall prospect by Baseball America. The former Philadelphia Phillies prospect and League City native has some of the best stuff and one of the most lively arms in the Astros’ organization. If he succeeds, he could pair with 22-year-old righthander Jordan Lyles in the club’s rotation during future years.

“He’s got a great arm. And I think as the season went on he started realizing how to use it,” said Astros rookie outfielder Marc Krauss, a recent OKC teammate of Cosart’s.

Lefthanders Dallas Keuchel and Erik Bedard will follow Cosart against the Rays during the Astros’ final series before the All-Star break.

Cosart went 0-1 with an 8.22 ERA during spring training. He started strong but struggled with his command and control. A key March 4 start against Detroit saw the righty give up four hits, three runs and four walks in just two innings.

“I talked to the (Oklahoma City) coaches the other day. He still has a lot to learn,” Astros pitching coach Doug Brocail said. “More so, from what I’ve been told, physically he’s ready. … I’m looking forward to seeing what the kid has. I know his arm’s incredible. But I want what’s above the shoulders to go with it.”

Cosart’s promotion has multiple effects. It brings more clarity to Harrell’s demotion, puts the remainder of the Astros’ starters on notice, gives the club a possible out if one or more starting pitchers are traded – Bud Norris, Harrell and Bedard are candidates – and represents the next wave of the club’s rebuild.

With Cosart called up, shortstop prospect Jonathan Villar could join the team in August, while a September promotion for center fielder George Springer is an increasing possibility.

Baseball America’s scouting report on Cosart: Cosart has a live, quick arm that produces a hard sinker that sits at 94-97 mph and touched 99 in the AFL. His fastball has excellent life down in the zone, which produces plenty of ground balls but makes the pitch tough to control. He excels at keeping the ball in the park, and he nearly got as many double plays (18) as he allowed extra-base hits (26) in 2012. Cosart throws his curveball with power, reaching 81-82 mph with good shape, and his solid straight changeup plays off his fastball well. Better command of his curveball would produce the strikeouts expected of a pitcher with such electric stuff.